The passage of sediment from mountain source to ocean...
Transcript of The passage of sediment from mountain source to ocean...
The passage of sediment from mountain source to ocean sink:
Results from the MARGINS S2S Waipaoa Sedimentary System, Hikurangi Margin
Alan Orpin & Source-to-Sink WSS Team
Photo: James Syvitski
Source-to-sink: a God’s-eye view
Canyon’s bypass slope
Intraslope sources
Closely-coupled catchment and
deep ocean sink e.g. Sepik, Var
Weak tectonic Dominant glacio-eustatic
Strong tectonic Weaker glacio-eustatic
Weakly-coupled catchment and deep ocean sink, shelf capture e.g. Amazon
Peak discharge
10x
Peak discharge 100-1000x
Submarine fans
Slope gradient and length
(Figure modified after Sømme et al., 2009)
Slopeward transfer driven by prograding clinoforms
4
Anthony the Anthropocene
Waipaoa, Waiapu
Waipaoa River mouth. Photo: James Syvitski
“… develop a quantitative understanding of margin dispersal systems and associated stratigraphy, so that we can predict their response to perturbations, such as climatic and tectonic variability, relative sea-level change, and land-use practices”. (Excerpt from MARGINS Source to Sink
Executive Summary)
► Emphasis on quantification of processes and linkages ► Terrestrial and marine
► Limited to the last-glacial cycle, but emphasis on
Holocene and Anthropocene records
(Image courtesy Josh Mountjoy)
Taupo Volcanic Zone
NE rain
Poverty Bay study area
Southern Ocean swell
Why the Waipaoa?
Waipaoa because… 1. Dramatic landscape responses to drivers
2003
1958 1939 (Aerial photos C/- Landcare Research)
2008
(Photo Phaedra Upton, GNS Science)
Dramatic changes in catchment behaviour: millennial scale
Berryman et al. (2010) ► Up to 50% of the post-glacial
downcutting achieved between 10-8 ka ► Rapid upstream migration (~2 km/ka) of
several major knickpoints Upton et al. (2013) ► LGM conditions more erosive compared
to Holocene
(Figure modified after Berryman et al., 2010)
Waihuka tributary of upper Waipaoa
Strong climate and environmental signals: event scale (10-2 to 102 y)
Lake Tutira catchment Post-cyclone Bola, 1988 (photos courtesy of Noel Trustrum)
1988 (Cyclone Bola)
1985
1977
1960
1973
1938
LTF9 –frozen box core (after Page et al., 1994)
► Gomez et al. (2011, 2013) - global climate teleconnections.
► Orpin et al. (2010) - intra-lake deposits and non-climate triggers.
Event strata (10-3 y timescales)
Low density, fine-grained upper surface
Low density mottled, weakly bioturbated?
Laminae, hummocky cross-stratification
0 cm
5 cm
10 cm 40
30
20
10
0
Dep
th c
m
(X-radiograph courtesy Rose & Kuehl, 2010)
Bola-style event (Lila Rose Pierce & Steve Kuehl, PhD thesis)
Cyclone Bola event, shelf core
July 2010 storm, shelf core
Oceanographic tripods
36 m
55 m
48 m
Figure after Richard Hale et al. (submitted, Special Issue of CSR) Oceanographic data courtesy of UW
1 in 8 yr flood
Depositional events ~10 cm deposit
Erosion?
Coherence of event drivers: an annual view
(Image courtesy Josh Mountjoy)
MD063003 MD063002
MD063008 MD063009
TAN0810-9
TAN0810-5 TAN0810-2
TAN0810-3
Cores show loss of terrestrial event fidelity in deepest ocean, BUT a turbidite record
► Cascadia Margin template (see Goldfinger et al., 2007)
► Cores cross-correlated
► Demanding of sophisticated
age-models
► Synchronicity of events
► 73 synchrononous turbidites
► 5-fold reduction in slope
sedimentation since LGM
► Hyperpycnites and debris flows rare
► Earthquakes most plausible trigger
► Poverty re-entrants return times c.
150-400 yrs
► Subduction interface earthquakes c.
800 yrs
Characterising Hikurangi Margin turbidites since the LGM
Pouderoux et al. (2012a, b)
After Hugo Pouderoux et al. (2012a, b) - Marine Geology and Natural Hazards and Earth System Science.
(Figures modified after Gomez et al., 2007; 2013; and in prep)
Cores allow inter-basin millennial-scale correlation through system
Shelf Lower floodplain
Upper floodplain
► Cycle of perturbations and landscape recovery
► Importance of landscape pre-conditioning
► Instantaneous and century-length scales for
“events”
► Human activity has had most profound impact on
late Holocene sedimentation
Catastrophic floods
>M7 earthquakes
Landscape recovery post-Taupo
Closure of shelf sediment budgets (pre-human)
Post-glacial basin geometry
Holocene accumulation
rates
(Figures after Gerber et al., 2010)
Last-century budgets and deposition on Poverty shelf
► Supply climate driven (floods) ► Big sediment signals ► At 102 yr timescales, perhaps only 25-50%
stratigraphically complete (Sommerfield, 2006)
Century-scale Century-scale
“Goldilocks Zone Sausage” of strata preservation
Mid-slope basin
Trough
Basin capture and transfer across the Poverty margin
Mid-shelf basin
Lower-slope basin
Near complete shelf capture (pre-human)
Capture & loss
MSC seismic profile
Active uplift
Active uplift
Imbricate thrust faults
Deformation front
avalanche debris Quaternary
shelf fill
Quaternary basin fill
3 km
2 km
1 km
Holocene riverine supply
Small %
Holocene budget: Gerber et al., 2010; Alexander et al., 2010; Orpin et al., 2006. Slope structure: Pedley et al., 2010.
Waipaoa 66%, 15%?
Waiapu 77%
Inflection point around 100 km shelf width
Off-shelf sedimentation dominates <20 km
Have anthropogenic impacts overwhelmed margin morphology as the dominant control on off-shelf sediment transfer?
Influence of shelf width and supply on off-shelf dispersal: have we tipped the scales?
91% Var
(Figures modified after Walsh & Nittrouer, 2003)
(Figure from Paquet et al., 2009)
Tectonic-sediment interactions over 150 ka timescales, upper Hikurangi Margin
Depocentre location controlled by:
► Eustacy <20-30 kyr timescales
► Tectonic deformation >100 kyr timescales
From mountain source to ocean sink: Waipaoa Sedimentary System
Supply Move + store capture + move capture + move
► Interconnectedness of source and sink, lithological coherence ► Ephemeral preservation of events, both marine and terrestrial
► Inter-basin fidelity at 101+ y timescales
► Utility of budgets: rates, tectonic-sediment interactions, and unknowns
► Marine paleoearthquake record
Figure from “Mountain source to ocean sink”, Special Issue of Marine Geology vol. 270, 2010